My dealer told me that a wake-up cable is not necessary anymore for a P40+ as it can be let awake all the time.
I asked for drawbacks like battery life or noise in the sensor but he replied that as for today he received no complaints.
I don't buy that completely.
Anyone already tested to shoot p40+/p65+ without wake-up cable ?
I am an architectural photographer and routinely use my P65+ in zero-latency mode on my Alpa STC.
There are several issues you need to be aware of.
Firstly, battery life is very substantially reduced. I carry up to 5 batteries with me but not everyone can afford the cost in both coin and weight of doing this.
On the upside, the back does boot very fast, so I usually only turn the back on when shooting, shutting it down between setups. With the IQ backs, bootup is instant, so this method is even easier to practice.
When shooting at sub-one-second exposures, the back has to be very warm to the touch before you notice any increase in noise. At longer exposures, the noise factor becomes apparent pretty quickly if you are starting your shot string with the back already warm. This becomes an issue more in summer, when high ambient temps mean the back cannot shed heat as quickly. When I was shooting in sub-zero temps in the Swiss Alps, I was shooting 2 min+ exposures without any heat or noise buildup.
Long story short, if you can be disciplined about shutting the back down, is is feasible to function without the wakeup cable, using zero-latency mode. If I think heat or battery life is going to be an issue (such as on multi-day hikes), then I use the wakeup cable.
I have investigated the Kapture Group solution and the older Alpa wakeup solution but didn't think the performance warranted the cost.
However, the new wakeup solution from Alpa is an absolute winner. It is a small, elegant looking device that screws into the cable release socket on the lens. It can be activated by either a conventional cable release or by hand. It offers the added advantage of being an ultra-soft-touch, and therefore low-vibration (read: less camera shake) shutter release button. I think this is a winner and I will be adding one to my kit as soon as I can.
http://www.alpa.ch/en/products/lenses/alpa-sync-solutions/alpa-sync-release.html
So, in short, it is entirely possible to bet by without the wakeup cable with the P40+ and P65+. However, it is a whole lot more convenient to have one and the best I have seen yet is the new Alpa Sync Release, link above.
Cheers,